Ink-jet printers comprise a plurality of interrelated components for printing on a print medium, such as paper. For example, the print zone of the paper is supported on a platen, and a print cartridge, secured in a bidirectionally movable carriage, prints characters on the paper in the print zone through a printhead in the cartridge.
There are several aspects of the printing that must be controlled to achieve consistency in printing from one sheet to the next and from one sheet thickness to another. For example, the printhead-to-paper space must be controlled, as must the printhead-to-paper angle.
The carriage moves on a shaft substantially parallel to the print zone, and the degree of parallelism must be controlled in order to assure uniformity of print across the sheet of paper. Further, the print medium is moved through the print zone by means of a drive roller mounted on a drive shaft. This drive shaft should also be maintained parallel to the print zone. Finally, the printer must be able to maintain the paper flat against the platen and deal with cockling of the paper, which occurs due to the presence of wet ink. Cockling tends to cause the gap between the paper and the printhead to vary.
The presence of wet ink on the medium requires special attention. Until the ink is dry, physical contact with the ink may result in smearing. However, physical contact with the print medium is usually required to remove the medium from the printer. This problem is usually addressed by adding a dryer or by reducing the print zone to allow for a contact area.